Transmitter



l May 27, 1930.-

H.'F.'FRUTH l TRANSMITTER Fi1ed sept. 16. 1926 155:41. All r ldllllldl,

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' Patented May ,27, 1930.

. tions inthe combinedor effective resistances UNITED ls'rfrlzsPATENT/OFFICE HAI. FREDERICK ERI'ITII, OE CHICAGO, ILLINOIS, ASSIGNQR ToWESTERN ELECTRIC COMPANY, INCORoRaTEI), -OE NEW YORK, N. Y., .eCORPORATION or NEW YORK TRANSMITTER Application led September 1 moreparticularly to a variable resistance apparatus for4 telephonetransmitters.

The primary object of this invention is to provide a simple, compactand'eiiective current varying means for electrical transmitters. ,f I

In accordance with the general features the invention contemplates thecooperation of a plurality of electrical conductors of differentresistance values and differently affected by a vibration responsivemeans to roduce variathereof. One embodiment of the inventioncontemplates a current varying device which forms a part of atransmitter circuit and comprises a low resistanceconductor, such Vas ablock of suitable conducting material fixed within the transmitterhousing and a high re' sistance stripv adapted to make contact invarying degrees with the 'conductor bloc'k.

,The high resistance strip is so connected with the transmitterdiaphragm that the vibrations of the diaphragm will be imparted thereto,causing the strip to vary its contact with the low'resistance block,short circuiting portions of the strip, and thereby producing variationsv in the combined- Or effective resistance of they' strip and the block1n accordance with the vibrations of the diaphragm. The invention iscapable' of many other applicationsand some alternative formsthereof'are disclosed in the accompanying drawings.

These and other objects will be more apparent from the followingdetailed descrip'- 'tion and theaccompanying drawings, where- Fig. lis acentral, vertical, sectional view of a transmitter provided with acurrent varying view of the device which is representative of oneembodiment of the invention; ,I

' Fig. 2 is a transverse, vertical, sectional transmittertakenon theline 2-.2

ofrFig.1; I A Fig. 3 is acental, vertical, sectlonal view,

of a current varying device which represents A `an alternative-form ofthe invention;

Fig. 4 isa similar-,sectional view of a curient support for thediaphragm 6, 1926. i .Serial No. 135,7523.v

Fig. 5 is another form of the invention, disclosing a pair of diaphragmscoupled with acurrent varying device. ,i Referring now to the drawingwherein like numeralsv have been vemployed .to designate similar partsthrough the various figures it will be observed that the numeral 10 inig. 1 is employed generally'to indicate a telephone transmitter. Thistransmitter comprises a mouthpiece 11 which is threaded'upon a housing12. Threaded within the housing 412 isa cylindrical ,casing or shell 14Which-'is `closed at its inner end, its lopposite fend bef l phragm18 ofduralumin, aluminum or other suitable material. These .rings 17 may beconstructed of felt, rubber or other `suitable l I materialwhich willsupply the properresil- 18D n l Acurrent varying means of the, typedis`closed in Fig. lconip'rises a semicylindrical low resistance block 20-olf suitable conducting -Inaterial Asuch as a block of carbon or thelike which is secured within the casing; 14 by means of brackets 21.-21Fig. 2). A high .re-V

-sistance strip 22 of conducting material such as gold foil, tant-alum,'platinum or other ma- -terial partiallyencircles the conductor block420 and is connected at its ends to the diaphragm 18 The curved portionof the strip 22 lies immediatelyadjacent'the curved surface of the.block 20 and it will be understood that f any outward movement ofl thediaphragm 18fwillcause the strip 2.2v to be carried more intimatel intocontact fwith 'the'` `adjacent curvedsur ace of the block." Like# wise,anyinwardmovement of the'diaphragm 18 will cause thestrip to becarriedawayv from Acontact with the block. A screws24 which is threadedcentrally of thelosedfend of the casing' '14 engageswith the medialpoint of the strip 22 'so as to hold the strip inontact at rent varyingdevice wherein the high .tone point and in 'a iixedrelation with th anceelement serves as thev diaphragm, and

block 20. `The screwg24also provides a -terl these terminals beingvconnected with wire leads which pass through an opening 23 in the rearcentral portion of the housing 12.

-The terminal of one of the leads may be secured in position -by meansof the screw 24 and the terminal of the other wire lead may be solderedto the diaphragm 18 or secured in any other suitable manner. i

From the foregoing it will be clear that u on the outward movement ofthe fdiap ragm 18 a certain portion ofthe high resistance strip 22 willbe short circuited by being carried more into contact with the block 20associated therewith and this short circuiti ing will eii'ectively varythe combined resistanceof the strip and the block and hence vary theamount of current flowing through the transmitter circuit. The amount ofshort circuiting or resistance variation eiected by the movement of thestrip 22 'will be in accordance with and responsive to the vibrationsexperienced by the diaphragm 18 enter- 11. y Referring to Fig. 3 wherean alternate form of the current varying device disclosed in Fig. 1 isshown, it will be observed that a cy.- lindrical casing 25 and aclampingring 26 similar to the casing 14 and clamping ring 15 shown in Fig. 1,has a diaphragm 28 constructedof duralumin, aluminum or the like andelastic supporting rings 29 clamped therebetween. Extending transverselywithin the casing 25 are a palr of low resistance ing the mouthpiecevconductor blocks 31 which are separated at their medial point by aninsulating member 32.A One l,of the surfaces of each ofl these blocks31'is slightly tapered and disposed immediately-adjacent these taperedsurfaces is a flexible high resistance strlp 33 of conductin materialsuch as one of the non-corrosive no le' metals which is clamped at itsextremities between the outer ends of the blocks 31 and the innersurface of the wall of the casing 25. .The extremities of the strip 33are electrically connected with the Iterminals of wire leadswhichpassthrough openings 34 provided inthecasing 25 by means fsolder or in anyother suitable manner. Interposed betweenthe medial portions of thestrip 33 and the diaphra m 28 is a connecting member 36 and '1t wi l beapparent that this 'connecting member will serve to impartvibrations'from the-diaphragm 28 to the strip 33.

Thecurrent varying mechanism, just described, functions very similarlyto the mech-v anism disclosedin connection withv Fig. 1.

' thestrip 33 will be effected andthe resistance As the high' resistancestrip 33 is caused to move inwardly and thereb to be carried moreintimately into contact w1th the tapered sur` face ofthe blocks 31. theshort circuit-ing .of

of` the transmitter` circuit correspondingly lowered. This variation inthe elective resistance of the strip 33 and the blocks 31 will cause arelative variation in the current flow and these changes willbe'directly responsive to and in accordance with the vi V brations ofthe diaphragm 28. xThe structures disclosed in Fig. 4 are similar tothose disclosed in Fig. 3, the only difference being that in Fig. 4 thediaphragm 28 and the co'nnecting member 36 are not present and the highresistance strip 33 has a double function, serving in contact withopposite sides of the strip 37 and is secured inthe wall of the casing38 Y `and uponthe vibration'of the diaphragms 40 the members 42 willbecarried into more or less intimate contact with-the strip 37. Thecontaeting ofthe members 42 with the strip 37 will result in aresistance variation 'which will relatively affect the amount of currentiow in the circuit and it will be noted-that in this instance, the highresistance strip is the' stationary element while the low members aremovable.

The types ot current varying devices hereinbefore described may be madevery compact and-by reasonof 'their compactness a transmitter. may berelatively small-'in size 'and convenient to handle. By reason of thefact that the movable parts are very light a transbot-h as a vibratorydiaphragm and also as a positive current conducting element mitter ogEthel type disclosed will approach a condition of free, undampedvibration which is necessary or'high eiiciency and quality;

Although the invention has beende'scribed in connection with a certaintype of telephoneI transmitter, it should be understood that the'current varying means may have many other applications and the inventionis limited only bythe scope of the appended` claims.

What is claimed is: 1. In a transmitter,

a housing, a low resistance conductor block fixed within the housing andprovided with an arcuate contact surface, a flexible hi h resistanceconductor strip connected with t e diaphragm and secured'to the blockmedially of the arcuate surface, the strip being o erable in response tovibrations of the aphragm to vary its contact with thesurface of theblock and thereby vary the eiective resistances of ythe elements.. l

2. In atr'ansmitter, a vibratory diaphragm, a fixed lowresistance-element providedwith 'an arcuate vContact surface, a' supporttherefor, anda high resistance element of very 10W mass substantiallyenclosingthe arcuate surface of the low resistance element and havingboth of its ends vfastened to the diaphragm, the high resistance elementbeing operable in response to vibrations of the dlaphragm to vary itsContact vwith the W resistance elesurface and operable in response tovibrations i ment to effect variations in their effective resistance. i

3. In a transmitter, a vibratory diaphragm, a stationary 10W resistanceblock having an arcuate contact surface, and a high resistance foil ofvery 10W mass partially encircling the low resistance block and havingits ends fastened to the diaphragm, the foil being secured to the blockmedially of the arcuate of the diaphragm to vary the effectiveresistance 'of the block and the-foil;

In Witness whereof, I hereunto'subscribe ryname this 3rd day ofSeptember, A. D.`

HAL FREDERICK FRUTH.

